Point license badge to license heading

[MichaelCurrin]

This might break a pattern of people expect, but can be what I want to do which is fine.

Maybe make a choice between the heading or the file.

If the section only contains a link to the file, then maybe the heading is not even needed. But by convention it seems to appear anyway in others' repos.

Also it is useful for being clear than a badge and if details are needed.